1. Field of the Invention
The present invention relates to a process of manufacturing a secondary powder composition and a molded body, both of which have a nanocrystalline structure.
2. Description of the Related Art
Nanocrystalline materials are polycrystals having a crystal size on the order of a few nanometers. Such materials are known and are described, for example, by H. Gleiter and P. Marquart in Z. Metallkunde [Metallurgy], Volume 75, No. 40 (1984) pages 263-267 and by R. Birringer, U. Herre and H. Gleitner in Proc. JIMIS-4, Trans. of Jap. Inst. of Metals, Volume 27 (1986) pages 43 et seq, the disclosures of which are herein incorporated by reference. The structure of these materials which are polycrystals is essentially characterized by the fact that the crystallites have a size ranging from 1 to 10 nm. Thus, the volume percentage of incoherent interfaces for these materials is comparable to the volume percentage of crystalline regions, that is, these materials consist of about 50 vol% crystals (crystalline component) and 50 vol% grain-boundaries (interfacial component). In the interface regions, the atom arrangement on the macroscopic average has neither a long-range nor a close-range order and, thus the material has a gas-like character. Materials having a nanocrystalline structure constitute a novel solid state different from glasses and crystals. The properties of nanocrystalline materials differ from the properties of the same material in the crystalline and/or glassy state.
The above publications also mention processes for manufacturing nanocrystalline powders and their compaction into molded bodies. The most frequently used powder production processes for manufacturing nanocrystalline powders include: atomization in an electric arc, evaporation in an inert atmosphere or evaporation in a vacuum with subsequent isoentropic relaxation. The powders are collected in a recipient vessel and compacted in the same recipient vessel in a pressing matrix. These processes, however, are very expensive and are prohibitively expensive for the production of large quantities of nanocrystalline powder compositions and molded bodies.